Figure 2–2 Contours of seismic magnitude for which signals would be expected (with signal-to-noise amplitude ratio greater than 3.2, i.e. 10 dB) at three or more stations of the IMS primary seismic network (solid squares), from 90 percent of the events at the contoured magnitude or larger. The contour interval is 0.25 magnitude units. The detection threshold for Europe, Asia, North America, and North Africa is in the magnitude range 3.5 to 3 or lower. (Figure provided by the Center for Monitoring Research)



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